1. Field of the Invention
This invention relates generally to RF/microwave measurement techniques used in integrated circuit testing, and even more specifically to the use of microwave scattering parameters (S parameters) in such techniques.
2. Related Art
In the post 9/11 world, there is an increased need for and concern about enhanced security. The security of state of art electronics systems ranks high among these concerns. The United States Department of Defense (DOD) recognizes the importance of assuring the protection of vital components of electronics systems from tempering by hostile forces. The DOD has launched a number of programs, via the Defense Advanced Research Projects Agency (DARPA), to address the issue. DARPA's concern is that the ability exists to detect small changes that might deliberately be introduced into an integrated circuit for hostile purposes.
Modern integrated circuits (ICs) are very complex devices and different methods may be used to introduce hostile changes, which would not be detected immediately by ordinary electrical testing. For example, long delay electronic counters connected to disable circuitry could be introduced. Other changes to reduce electrical reliability by changing feature sizes may also be introduced.
Changes to an integrated circuit may occur at an untrusted stage of the design or manufacturing. The changes may include modifying the RTL (register transfer level), the netlist, the layout, the fabrication process, or even the silicon, for example, by using Focused Ion Beam (FIB) editing. An untrusted foundry may make logic insertions or modifications, or include IP cores, which contain parasitic features used to sabotage normal operations by changing delays, or disabling clocks or busses.
It might be desirable to identify particular integrated circuits, or parts of integrated circuits for the protection of intellectual property rights.
Therefore, a need exists for non-destructive methods to provide highly sensitive and selective detection of even very subtle modifications that appear anywhere in the IC lifecycle.